SmtpClientSslCipherAlgorithm Property

public override CipherAlgorithmType? SslCipherAlgorithm { get; }

public static void PrintSslConnectionInfo (string host, int port)
{
    using (var client = new SmtpClient ()) {
        client.Connect (host, port, SecureSocketOptions.Auto);

        Console.WriteLine ($"Negotiated the following SSL options with {host}:");
        Console.WriteLine ($"        Protocol Version: {client.SslProtocol}");
        Console.WriteLine ($"        Cipher Algorithm: {client.SslCipherAlgorithm}");
        Console.WriteLine ($"         Cipher Strength: {client.SslCipherStrength}");
        Console.WriteLine ($"          Hash Algorithm: {client.SslHashAlgorithm}");
        Console.WriteLine ($"           Hash Strength: {client.SslHashStrength}");
        Console.WriteLine ($"  Key-Exchange Algorithm: {client.SslKeyExchangeAlgorithm}");
        Console.WriteLine ($"   Key-Exchange Strength: {client.SslKeyExchangeStrength}");

        // Example Log:
        // 
        // Negotiated the following SSL options with smtp.gmail.com:
        //         Protocol Version: Tls12
        //         Cipher Algorithm: Aes128
        //          Cipher Strength: 128
        //           Hash Algorithm: Sha256
        //            Hash Strength: 0
        //   Key-Exchange Algorithm: 44550
        //    Key-Exchange Strength: 255

        client.Disconnect (true);
    }
}